The present invention relates to a safety restraint system for use in motor vehicles. In particular, the present invention is directed to a weight sensor for generating a signal indicative of the weight of a person or object seated or located in a vehicle seat.
Safety restraint systems are used in motor vehicles for protecting the vehicle occupants during collisions. In addition to seat belts, many safety restraint systems now include a driver-side air bag mounted in the steering wheel and a passenger-side air bag mounted in the dashboard. Furthermore, recent attention has been directed to incorporation of other restraint devices such as, for example, side air bags, seat belt pretensioners, and energy management retractors into the safety restraint system. Many, if not all, of these restraint devices are activated by the vehicle's crash management system in response to detection of a vehicular collision exceeding a predetermined impact magnitude.
In order to optimize occupant protection during a collision, it is desirable to vary the deployment characteristics of the air bags and/or the operational characteristic of the other restraint devices based on various control parameters, such as the severity of the crash, belt usage, and the position and size of the seated occupant. Thus, the vehicle's crash management system includes various sensors for detecting and/or measuring such control parameters. One particular control parameter that is useful for regulating the output characteristics of the restraint devices is the weight of the seated occupant. As such, a need exists to develop a weight sensing device for use in safety restraint systems.
Accordingly, the present invention is directed to a weight measuring device for incorporation into the crash management system of a motor vehicle's safety restraint system. This objective may be achieved by providing a weight sensor which is sensitive to the magnitude of a displacement of a sensor part caused by an occupant sitting in a vehicle seat and which is indicative of the occupant's weight.
In accordance with the teachings of the present invention, a weight sensor is provided for measuring the weight of a seated occupant. The weight sensor is mounted between the seat frame and the seat mounting structure or between the seat mounting structure and the vehicle floor or within the seat cushion. The weight sensor is comprised of an enclosed housing assembly and a position sensing unit mounted within the housing assembly. The position sensing unit includes a Hall effect sensor fixed in the housing assembly and a permanent magnet mounted to a flexible portion of the housing assembly. In operation, the weight of the seated occupant or object deflects the flexible portion of the housing assembly. As the flexible portion deflects in response to the weight of the object or occupant, the position of the magnet relative to the Hall effect sensor changes to generate a relative change in the sensor output. Upon calibration of the system, this positional variation provides an indication of the weight of the occupant or object. Thus, the position sensing unit generates an output signal which is proportional to the amount of deflection which, in turn, is indicative of the occupant's or object's weight. As can be appreciated, the weight sensor, and its associated electronics, can also provide an indication that no object or occupant is located in the seat.